A composite image showing the progression of a partial solar eclipse over the Washington Monument, in Washington, D.C., the U.S., April 8, 2024. /NASA
A chilly, midday darkness fell across North America on Monday as a total solar eclipse raced across the continent, thrilling those lucky enough to behold the spectacle through clear skies.
The eclipse's path of totality stretched from Mazatlan, Mexico, to Newfoundland, an area that crosses 15 U.S. states and is home to 44 million people. Revelers were engulfed in darkness at state parks, on city rooftops and in small towns.
Where clear skies prevailed, observers along the direct path of the eclipse were treated to the rare spectacle of the moon appearing as a dark orb creeping in front of the sun, briefly blocking out all but a brilliant halo of light, or corona, around the sun's outer edge.
It was the first total eclipse to sweep across a large swath of North America since 2017, and it marked the last such occurrence visible from the contiguous United States until 2044.
Mexico's beachside resort town of Mazatlan was the first major viewing spot for totality. Thousands in solar-safe eyewear perched in deck chairs along the coastal promenade, and an orchestra played the "Star Wars" movie theme as skies darkened under the approaching lunar shadow.
The crowds burst into cheers, applause and whistles when the eclipse reached totality.
The period of totality, lasting up to 4-1/2 minutes depending on the observer's location, was ushered in by a number of other eerie eclipse effects. Some stars twinkled at midday as dusk abruptly descended, sending temperatures dipping and faint waves of "shadow bands" flickering over the landscape. Birds and other wildlife sometimes fall silent and still.
A partial eclipse, in which the moon obscures only a portion of the sun, was visible across most of the continental United States outside the path of totality, where weather permitted.
"This may be the most viewed astronomical event in history," said National Air and Space Museum curator Teasel Muir-Harmony.
Experts from NASA and scores of universities were posted along the route, launching research rockets and weather balloons and conducting experiments.
How does a solar eclipse occur?
A solar eclipse occurs when the moon passes between the sun and the Earth, casting a shadow over parts of the Earth and blocking the face of the sun for observers in those locations. /NASA
A solar eclipse occurs when the sun, moon and Earth are aligned with the moon in between.
A total solar eclipse takes place when the moon completely blocks out the sun's light. An annular eclipse happens when the moon is farthest from Earth as the moon seems smaller and doesn't block the entire view of the sun, and a partial solar eclipse occurs when the sun, moon and Earth are not perfectly lined up, with only a part of the sun to be covered, according to NASA.
"Because Earth's surface is curved, sometimes an eclipse can shift between annular and total as the moon's shadow moves across the globe. This is called a hybrid solar eclipse," said NASA.
How to watch a solar eclipse safely?
During totality, when the sun is completely shrouded, it's fine to remove your glasses and look with your naked eyes.
But before and after, certified eclipse glasses are essential to avoid eye damage. Just make sure they're not scratched or torn.
Cameras, binoculars and telescopes must be outfitted with special solar filters for safe viewing.
Bottom line: Never look at an exposed sun without proper protection any day of the year.
When's the next total solar eclipse?
Full solar eclipses occur every year or two or three, often in the middle of nowhere like the South Pacific or Antarctic. The next total solar eclipse, in 2026, will grace the northern fringes of Greenland, Iceland and Spain.
North America won't experience totality again until 2033, with Alaska getting sole dibs. Then that's it until 2044, when totality will be confined to Western Canada, Montana and North Dakota.
There won't be another U.S. eclipse, spanning coast to coast, until 2045. That one will stretch from Northern California all the way to Cape Canaveral, Florida.
What to expect next in April?
April 21: A Halley-type comet, known as 12P/Pons-Brooks, will make its closest approach to the sun and could be visible to naked eyes with its brightness largely increased.
April 22: The Lyrids meteor shower will reach its peak.
April 23: A full moon, also known as the "Pink Moon," which symbolizes the beginning of spring, will rise.
(With input from AP, Reuters)